Polymerization of phenylacetylene and of p-tolyl-acetylene catalyzed by beta-dioxygenato rhodium(I) complexes in homogeneous and heterogeneous phase

The catalytic polymn. of phenylacetylene and p-tolyl-acetylene under homogeneous and heterogeneous conditions is described. The catalysts used are either (cod)Rh(AAEMA) [cod: 1,5-cyclooctadiene, AAEMA-: deprotonated form of 2-(acetoacetoxy)ethyl methacrylate] or the supported metal complex obtained by thermal copolymn. of (cod)Rh(AAEMA) with suitable comonomer and cross-linkers. Complexes of general formula (diene)Rh(acac) [diene: 2,5-norbornadiene (nbd) or 1,5-cyclooctadiene (cod)] have also been used for comparison. High yields in poly(aryl-acetylene) are achieved in the homogeneous phase for both substrates using THF as solvent at room temp. even in the absence of any co-catalyst. The use of the supported rhodium(I) catalyst facilitates the polymn. of arylacetylenes yielding, in the case of poly(phenylacetylene) (PPA), a polymer having high stereoregularity and higher mol. wt. respect to that obtained in homogeneous phase. A new correlation between IR data and the cis-percentage of PPA is proposed and discussed